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package com.oracle.truffle.runtime;

import java.util.Objects;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.nodes.LoopNode;
import com.oracle.truffle.api.nodes.RepeatingNode;

abstract class AbstractOptimizedLoopNode extends LoopNode {

    @Child protected RepeatingNode repeatingNode;

    @CompilationFinal private long trueCount; // long for long running loops.
    @CompilationFinal private int falseCount;

    protected AbstractOptimizedLoopNode(RepeatingNode repeatingNode) {
        this.repeatingNode = Objects.requireNonNull(repeatingNode);
    }

    @Override
    public final RepeatingNode getRepeatingNode() {
        return repeatingNode;
    }

    protected final void profileCounted(long iterations) {
        if (CompilerDirectives.inInterpreter()) {
            long trueCountLocal = trueCount + iterations;
            if (trueCountLocal >= 0) { // don't write overflow values
                trueCount = trueCountLocal;
                int falseCountLocal = falseCount;
                if (falseCountLocal < Integer.MAX_VALUE) {
                    falseCount = falseCountLocal + 1;
                }
            }
        }
    }

    protected final boolean inject(boolean condition) {
        if (CompilerDirectives.inCompiledCode()) {
            return CompilerDirectives.injectBranchProbability(calculateProbability(trueCount, falseCount), condition);
        } else {
            return condition;
        }
    }

    private static double calculateProbability(long trueCountLocal, int falseCountLocal) {
        if (falseCountLocal == 0 && trueCountLocal == 0) {
            // Avoid division by zero and assume default probability for AOT.
            return 0.5;
        } else {
            return (double) trueCountLocal / (double) (trueCountLocal + falseCountLocal);
        }
    }
}
